Conventionally, a cable used for wiring of a drive member for an industrial robot depends solely on a pure copper conductor, and bending durability required as the cable for the robot is ensured in terms of both (i) a cable design technique in which a combined structure of strands of the pure copper conductor is optimized and (ii) a cable manufacturing technique in which a diameter of the pure copper conductor is decreased to an optimal diameter by a wire drawing method and the pure copper conductor is coated with a optimally-selected polymer coating material. With a recent increase in speed of motions of the robot, there is a strong need to make the cable for the robot lighter in addition to the bending durability.
Patent Literature 1 discloses, as a copper or copper alloy clad aluminium alloy wire that is lightweight and highly conductive and has better wire drawing workability than a copper clad aluminium wire, a copper or copper alloy clad aluminium alloy wire including (i) a core made of a high aluminium alloy wire (e.g., Al-0.4Mg-0.4Si) with tensile strength of 24 kgf/mm2 or more and a conductivity of 58% IACS or more and (ii) a copper or copper alloy layer coating the core with a stacking factor of 10 to 20%.
Patent Literature 2 discloses, as a conductor used for an electric wire for an automobile, made of a copper clad aluminium composite strand lighter than a copper wire, and has good flexibility and good tensile strength, a conductor including (i) a core made of an aluminium-magnesium alloy containing 2.2 to 5.6 mass % magnesium, (ii) an intermediate layer made of copper or a copper alloy, which is laminated on an external side of the core, and (iii) a reinforcement layer made of nickel or a nickel alloy, which is laminated on an external side of the intermediate layer. A diameter of the whole conductor is 1.5 mm or less. A cross sectional area of the reinforcement layer is 3 to 10% of that of the whole conductor.
Patent Literature 3 discloses, as a copper clad aluminium alloy wire having flexibility, workability, good wire drawing workability, high conductivity, and tensile strength, a copper clad aluminium alloy wire including an aluminium alloy wire coated with copper, in which the aluminium alloy wire is made of an aluminium alloy, containing 0.2 to 0.8 mass % Si, 0.36 to 1.5 mass % Fe, 0.2 mass % or less Cu, 0.45 to 0.9 mass % Mg, 0.005 to 0.03 mass % Ti, and Al and inevitable impurities for the rest.